Abstract: A method for constructing multi-output orthogonal Boolean functions is presented. For any given integers n,m(n≥m), and the balanced function f(x) onalphabet set, m balanced functions can be obtained by using bifurcate tree. Furthermore, arbitrary linear combination of these functions is balanced. i.e. We get a nvariable moutput orthogonal function. The enumeration of the functions are also given.

Key words: orthogonal Boolean function, enumeration, balanced function, bifurcate tree